September 2014 - Picture of the Month
NGC 6888 The Crescent Nebula in Cygnus
Image Courtesy of David Davies, Cambridge, UK. Please click on the image for the high resolution version.
For more images from David please visit his Flickr Photostream.
It's been a little while since I've shared anything from the deep sky. I managed to be away during several of the clear nights we've had recently.
My observatory was completed just over one year ago and the first object I observed from it was the Crescent Nebula. It seemed fitting to return to it this year and see if I could do any better.
So I've spent several nights during August (17, 28 and 31) gathering narrow band data on the Crescent Nebula and further time learning how to process narrow band images. The attached is the result.
I now have the benefit of automatic focussing which is helping I think by enabling me to refocus by remote control during the night. I'm using a Lakeside focus motor and the Scopefocus application from Kevin Sipprell in the US that works with my image capture software, Nebulosity.
Viewing conditions were almost universally poor with poor transparency and high thin cloud. This image comprises 100 minutes of H-alpha and 200 minutes of OIII data in 20 minute subs, five hours in total, captured with a 254mm Newtonian and QSI 583 camera equipped with 3nm Astrodon filters.
Processing was done in Pixinsight where H-alpha was assigned to red, OIII to blue and a synthetic green was generated using 85% blue and 15% red. I did try to combine the H-alpha and OIII with a normal green image and the result was just awful.
I'm fascinated by this object. The great bubbles of OIII extend well beyond the normally visible object and are also evident throughout its internal structure.
I'm continuing to capture RGB data and it would be interesting to see if I can combine the RGB and narrow band data in the future.